Propolis is known as a sticky substance which is used to build beehives. It is believed that intact propolis contains a variety of trace ingredients in the form of a homogenous mixture with resins, beeswax, essential oils and pollens as predominant ingredients. Since ancient times propolis has been used as a folk remedy in different areas of the world because of its potential antimicrobial and soothing and demulcent activities.
Shinobu Matsuda, in Foods and Food Ingredients Journal of Japan 160:64-73, 1994, discloses that other ingredients, such as flavonoids and phenol carboxylic acids, have been isolated from propolis and identified. With the advances in identification and clarification of particularly ingredients and their biological activities, the usefulness of propolis has been emphasized. As a result, a variety of health care and supplemental health care products have appeared in the market.
Intact propolis is not useful in food products because it generally contains large amounts of contaminants and is barely soluble in water. In commercial health care and supplemental health care products, propolis is added in the form of extracts which are obtained by soaking crushed propolis in ethanol, glycerol, and/or water. Propolis has a peculiar odor, which is one of the drawbacks to be overcome. However, currently available propolis extracts still have this peculiar odor, so that they can only be used in a few types of food products.
Japanese Patent Kokai Nos. 165,595/89 and 316,968/93 disclose several approaches to improving the appearance and smell of propolis extracts using activate charcoal, synthetic porous absorbents, and cation exchange resins. Unfortunately, each of these approaches has proved to be unsuccessful in reducing the peculiar odor of propolis.